Valley Kondo Effect in Silicon Quantum Dots

TL;DR

This paper investigates the valley Kondo effect in silicon quantum dots, revealing complex spectral features and non-conservation of valley index, with implications for understanding spin-valley interactions and tunneling behaviors.

Contribution

It provides a theoretical analysis of the valley Kondo effect in silicon quantum dots, highlighting unique spectral signatures and the non-conservation of valley index during tunneling.

Findings

Complex peak structures near the Fermi energy in the density of states.

Valley index is generally not conserved during electron tunneling.

Features identified can help interpret experimental conductance measurements.

Abstract

Recent progress in the fabrication of quantum dots using silicon opens the prospect of observing the Kondo effect associated with the valley degree of freedom. We compute the dot density of states using an Anderson model with infinite Coulomb interaction $U$, whose structure mimics the nonlinear conductance through a dot. The density of states is obtained as a function of temperature and applied magnetic field in the Kondo regime using an equation-of-motion approach. We show that there is a very complex peak structure near the Fermi energy, with several signatures that distinguish this spin-valley Kondo effect from the usual spin Kondo effect seen in GaAs dots. We also show that the valley index is generally not conserved when electrons tunnel into a silicon dot, though the extent of this non-conservation is expected to be sample-dependent. We identify features of the conductance that should enable experimenters to understand the interplay of Zeeman splitting and valley splitting, as well as the dependence of tunneling on the valley degree of freedom.